While not limited thereto, the present invention is particularly adapted for use as an electroacoustic transducer in microphones. As is known, the usual microphone is of either the carbon type or the condenser type. In the carbon microphone, carbon granules are compressed to a greater or lesser degree by a diaphragm, so that their resistance varies with the acoustic pressure. This, in turn, produces corresponding fluctuations in the current which can be transmitted to a receiver. In the condenser microphone, on the other hand, a flexible diaphragm is utilized in conjunction with a fixed counterelectrode to form an air condenser whose capacitor varies with the vibrations of the diaphragm. Consequently, a direct voltage applied in the circuit has an alternating voltage superimposed on it corresponding to the sound waves impinging on the diaphragm.
Such microphones, while used extensively in the past, are essentially high input impedance devices and, consequently, require that the electrical signal derived from the carbon granules, for example, must be amplified extensively before it can be transmitted.